hi~  i received the key with the premium version, i was wondering if i had to paste the key code somewhere in the files or the game , or if it was arleady in the premium version of the game that i downloaded ? 

If you're using Android, go to the play store and then to the menu on the right with all your info and scroll down to Redeem, right under Account. Enter your code there and it'll download the paid version of the  game for you <3